A novel method for sensing local pressure inside a microfluidic device is proposed and developed. The main advantage of the method is that the pressure can be visually seen without attaching any electrical wire or instrument. The method can also be easily integrated into applications, such as micro-robots, because of its single-layer design. The working principle is based on the deformation of Polydimethylsiloxane, a kind of polymer that is often used in microfluidic systems. The deformation in the deformation chamber causes fluid to flow in, or out, the sensing area, and consequently results in changes of color intensity in the area. As a result, the pressure can be determined based on the brightness value over the sensing area. Experimental results show a highly correlated relationship between the measured brightness and pressure with the absolute correlation of 0.986. The hysteresis and drift of the proposed sensor are investigated, and are compared with our previously proposed microbeads approach. The prototype of the proposed sensor succeeded in performing measurement on local pressure in a microfluidic device with the resolution of 3.04 kPa.